Method and apparatus for inerting head space of a capped container

ABSTRACT

A process to reduce oxygen in the head space of non-pressurized containers comprises injecting an inert gas into the container head space and into the cap during the capping process. In an alternative embodiment, inert gas is injected into the caps at one or more points along the conveyance rout to the capping point.

TECHNICAL FIELD

This invention relates to bottling of potable fluids subject tomicrobial attack. In particular, the invention relates to a method andapparatus for extending the shelf life of such potable fluids stored innon-pressurized containers with snap-on caps by at least partiallydisplacing the oxygen in the cap and in the container head space with aninert gas.

BACKGROUND OF THE INVENTION

It has long been recognized that removing gaseous oxygen from sealedcontainers containing potable liquids can extend their shelf lives byreducing the rate of spoiling from microbial attack. Vacuum packagingand the use of bags have been used to eliminate gas altogether frompackaging, but inerting, or the filling of the unfilled container spacewith an inert gas, is also widely used.

In a popular method of inerting, a small dose of liquid nitrogen isinjected into a filled container just prior to capping. The nitrogenvaporizes, which displaces oxygen from the container's head space duringcapping. Some liquid nitrogen remains in the container after capping andvaporizes in the sealed container, which pressurizes the container.However, this method is not useful for non-pressurized containers suchas milk and juice bottles. The snap-on caps for these containers are notdesigned to withstand the pressures developed by the vaporized nitrogen,and the increased pressure created by the vaporized nitrogen breaks theseal between the cap and bottle, allowing air to be sucked back into thecontainer during handling and shipping, renewing microbial attack. As aresult, shelf life of non-pressurized capped containers is notsignificantly extended using this method.

Methods have been developed for inerting the head space innon-pressurized containers such as the classic gable-top papercontainer. U.S. Pat. No. 6,634,157 issued to Anderson et al. on Oct. 21,2003 discloses an apparatus and method for filling these containers. Itmakes used of a special nozzle inserted into the container after fillingwith product and prior to sealing the container. The inerting step mustbe carried out as a separate step between filling and sealing thecontainer, and therefore adds more time to the overall packaging cycle,which reduces throughput. Also, the apparatus for positioning, operatingand removing the nozzle is complex and relatively expensive.

A need remains for a inexpensive method and apparatus for inerting anon-pressurized beverage container. Such a method preferably should workwith established capping apparatuses and require a minimum of space forthe inerting apparatus. In addition, a method and apparatus that canperform the inerting without adding additional time to the overallfilling/sealing procedure would be considered advantageous.

SUMMARY OF THE INVENTION

In general, an invention having the desired features and advantages isachieved by injecting an inert gas such as nitrogen simultaneously intothe head space of a filled container and the cap used to seal thecontainer during the capping procedure. Preferably, the apparatus forinjecting the apparatus includes at least one injector oriented downwardat an angle between about fifteen and forty degrees from horizontal, andpreferably between about twenty and twenty-five degrees, and aimed intothe top of the container neck just at or before the point at which thecap initially contacts the container. The velocity of nitrogen flowshould be low enough to prevent splashing of container contents, andpreferably is low enough to avoid visibly disturbing the fluid surface.However, in every case the flow rate must be enough to reduce the oxygenlevel in the sealed container to an amount below about fourteen percentoxygen by volume, and preferably below about twelve percent by volume.While nitrogen is preferred for economic reasons, other inert gasesknown in the art can also be used.

An alternate embodiment of the apparatus employs separate injectors, onedirected into the container and another into the cap at or near thepoint where the cap engages the container. In yet another embodiment,inert gas is injected into the cap at more than one point along thecap's conveyance route immediately prior to engaging and sealing thecontainer. The flow rates for the different injection streams can beequivalent or differ substantially from each other.

The present invention has advantages over other methods and apparatusfor inerting. Less equipment and space is needed than for apparatususing an inert gas filled environment. The apparatus for carrying outthe method of the invention can easily be adapted to existing cappingequipment. The inerting process can be carried out between filling andcapping the container without adding any time to the overall process.Additional features and advantages of the invention will become apparentin the following detailed description and in the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front schematic elevation of a preferred apparatus used topractice the process of the invention.

FIG. 2 is a right side elevation of the apparatus shown in FIG. 1.

FIG. 3 is a front elevation for an alternate apparatus embodiment.

FIG. 4 is a front elevation for another apparatus embodiment.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 and 2 show a typical apparatus for capping one-gallon plasticmilk bottles. The apparatus 11 is shown in schematic with nonessentialequipment removed for visibility. Throughout the figures, which are notdrawn to scale, equivalent elements are given identical referencenumbers. While snap-on caps are shown, it is believed screw-on caps canalso make use of the method of the invention for low pressure service,i.e. service in which the pressure in the sealed head space can rangefrom slightly below to slightly above atmospheric pressure when capped,but not at high enough pressure to require a container with featuresdesigned to handle elevated pressure (e.g. bottles for carbonatedbeverages). Therefore, the term ‘cap having a top member and a skirtdepending from the top member and defining a skirt volume’ is intendedto include both the snap-on caps shown and screw-on caps.

A chute 13 is used to transport caps 15 to the bottles 17. Each cap 15has a top member 19 and a skirt 21 depending from the top member 19 anddefining a partially enclosed skirt volume 23 with the top member 19. Atthe end of the chute 13, a pivotable arm (not shown) holds the next cap15 to be used in the proper position for being put onto a bottle 17. Asthe bottle 17 moves along the conveyer track 25 past the cap 15, theskirt 21 engages the bottle 17. The moving bottle biases the cap 15 sothat it is released by the pivotable arm and passes under a plate 29that biases the cap downward, sealing it onto the bottle 17.

The apparatus 11 of the invention comprises a pair of injectors 31, 33made from nominal half-inch copper tubing mounted on a header block 35which in turn is attached by an adjustable linkage 37 to the chute 13.Flexible tubing 39 connects the header block 35 to a supply ofpressurized nitrogen, preferably through a control loop having a controlvalve and flow controller (not shown), although other schemes can beused such as manually operated throttling valve and a pressure gaugelocated between the valve and the header block 35. An alternativeembodiment is envisioned but not shown, wherein the header block 35 isabsent and the injectors 31 and 33 are individually supplied by flexibletubing or other suitable conduit to the pressurized inert gas supply.

Because the injectors must be located close to the chute 13, theinjectors 31 and 33 are separated by a gap 41 to allow tags 43 extendingfrom the caps 15 to pass between the injectors unobstructed. Whilesimple copper tubing is shown, other types of injectors known in the artcan also be used, including other cross sectional types such asdispersion fans. Jets and devices that produce a narrow gas stream arenot prohibited but are not preferred since a narrow, high velocity gasstream is more likely to produce splashing or otherwise disturb thesurface of the container contents. Regardless of the injector shape, acritical feature is the proper orientation of the injectors 31, 33 sothat the inert gas stream is directed at or just below the point wherethe cap skirt 21 initially engages the bottle, in order to ensure thatboth the bottle head space and the cap skirt volume are properly flushedby the inert gas. The adjustable linkage 37 allows the user toexperiment with orientation for best results with various equipmentmodels, when the apparatus 11 is retrofit on existing capping equipment.However, the adjustable linkage can be replaced with a fixed mountingbracket or other unadjustable hardware for a particular piece or modelof equipment or when manufactured as an integral part of the cappingequipment.

The flow of nitrogen is set from about fifty to about two hundredstandard cubic feet an hour (SCFH) to ensure the desired reduction ofthe oxygen level in the head space of a one-gallon milk container. Theinjectors operate continuously, so that there is some waste of the inertgas in the time interval between containers. The injectors are angled atabout fifteen to forty degrees from horizontal, and preferably fromabout twenty to twenty-five degrees from vertical, and oriented so thata significant part of the flow stream flushes the skirt volume 23. Thisis necessary because trials have shown that the gas trapped in the skirtvolume 23 tends to displace gas from the head space during cappingrather than being pushed out into the surrounding environment, so thatthe gas composition in the cap has a significant impact on the final gascomposition in the sealed head space.

FIG. 3 shows an apparatus for use with another embodiment of theinvention. This embodiment differs from the preferred embodiment in thatthe inert gas is injected separately into the head space and the skirtvolume by two independent injectors 45 and 47. While this apparatus alsoworks well, it is more sensitive to proper construction and orientationfor optimal performance. Therefore, this embodiment is better suited toa fixed installation as shown, rather then being adjustable, althoughadjustability can still be used. FIG. 4 extends the use of multipleinjectors even farther. In this embodiment, the inert gas is injectedinto the caps at more than one point along the delivery chute. The flowrates of the various injection streams can be set equal to each other,or varied as desired. Also, in the embodiments of FIGS. 3 and 4 it ispossible, although not shown, to use different inert gases for thedifferent injectors. For example, argon may be preferred for use influshing the head space, as argon is significantly denser than air andwill form a fairly stable and distinct layer within the head space, sothat filling the head space will effectively prevent oxygen in the airfrom settling back into the head space. While carbon dioxide will alsowork well from a technical standpoint, it is not preferred as it tendsto affect the taste of the container contents. Argon's density andtendency to stratify, which help when inerting the head space, workagainst it in attempting to effectively inert the skirt volume, which isinverted. Here, nitrogen may be more desirable, as it more nearlymatches the density of air, and does not stratify, so that it will tendto remain in the skirt volume longer.

In all the embodiments, the flow of inert gas is selected so that theoxygen level in the sealed container is less than about fourteen percentby volume, and preferably less than about twelve percent by volume. Bycontrast, the prior art does not mention any allowable upper limit foroxygen content, and generally implies that proper inerting requiresremoval of essentially all oxygen from the head space. The inventor hasdiscovered that practical extension of shelf life occurs even whenoxygen levels in the head space are as high as about fourteen percent,with shelf life increasing with decreasing oxygen level. As the oxygenlevel is reduced below six percent by volume, there is a diminishingreturns to how much shelf life is extended with reduced oxygen level.The discovery that the head space need not be flushed completely free ofoxygen makes the present methods and apparatus practical. For example,it is not necessary to insert an inert gas injector into the head spacein order to ensure complete flushing of the head space, so the apparatuscan be achieved without interfering with the conventional operation ofthe capping equipment, so there is no throughput penalty. Since completeremoval of oxygen is not required, there is no need to create anoxygen-free environment around the container during capping, whicheliminates the need for expensive, complicated and bulky apparatus forcreating an artificial contained atmosphere around the bottles.

The invention has several advantages over the prior art. The method canbe carried out simultaneously and independently of the conventionalcapping process, so throughput is essentially unchanged. The apparatusis simple and inexpensive to install, and requires relatively littlespace, especially in comparison to methods and apparatus that create anenclosed low-oxygen atmosphere surrounding the containers duringcapping. Existing capping equipment can be easily retrofitted topractice the method of the invention.

The invention has been shown in several embodiments. It should beapparent to those skilled in the art that the invention is not limitedto these embodiments, but is capable of being varied and modifiedwithout departing from the scope of the invention.

1) A method for extending shelf life of a potable liquid in a containersealed by a cap having a top member and a skirt depending from the topmember and defining a skirt volume, the container defining a head spaceabove the potable liquid, comprising the step of: a) bringing thecontainer and the cap into a close relationship; b) injecting an inertgas simultaneously into the container head space and the skirt volume;and c) sealing the cap on the container with a gas composition in thehead space comprising less than about fourteen percent oxygen by volume.2) A method as recited in claim 1, wherein the cap initially contactsthe container in an inclined orientation during the sealing step (c),and the inert gas is injected at or near the point where the cap and thecontainer initially come into contact during the sealing step (c). 3) Amethod as recited in claim 1, wherein the gas composition in the sealedhead space is less than about twelve percent oxygen by volume. 4) Amethod as recited in claim 1, wherein the inert gas is injected by atleast one injector, and the at least one injector injects inert gas intoboth the container head space and the cap skirt volume. 5) A method asrecited in claim 1, wherein the inert gas is injected by at least afirst injector and a second injector, the first injector injecting inertgas into the container head space and the second injector injectinginert gas into the cap skirt volume. 6) A method as recited in claim 5,wherein the same inert gas is injected by the first injector and thesecond injector. 7) A method as recited in claim 5, including a firstinert gas and a second inert gas, wherein the first injector injects thefirst inert gas into the container head space and the second injectorinjects the second inert gas into the cap skirt volume. 8) A method asrecited in claim 1, further comprising the step of injecting an inertgas into the cap skirt volume prior to the step (a) of bringing thecontainer and the cap into a close relationship. 9) A method as recitedin claim 5, wherein the gas composition in the sealed head space is lessthan about twelve percent oxygen by volume. 10) A method as recited inclaim 8, wherein the gas composition in the sealed head space is lessthan about twelve percent oxygen by volume. 11) An apparatus for usewith a method for extending shelf life of a potable liquid in acontainer sealed by a cap having a top member and a skirt depending fromthe top member and defining a skirt volume, the container defining ahead space above the potable liquid, the apparatus comprising: a) apressurized supply of an inert gas; b) means for injecting the inert gasinto the container head space, connected to the pressurized supply ofinert gas; and c) means for injecting the inert gas into the cap skirtvolume, connected to the pressurized supply of inert gas. 12) Anapparatus as recited in claim 11, wherein at least one injector is boththe means for injecting the inert gas into the container head space andthe means for injecting the inert gas into the cap skirt volume. 13) Anapparatus as recited in claim 11, wherein at least one first injector isthe means for injecting the inert gas into the container head space,further comprising at least one second injector for injecting the inertgas into the cap skirt volume. 14) An apparatus as recited in claim 13,further comprising a plurality of second injectors, positioned so as toinject the inert gas into cap skirt volume at more than one locationalong a route traveled by the caps prior to engaging with and sealingthe container. 15) An apparatus as recited in claim 14, furthercomprising a second pressurized supply of inert gas connected to themeans for injecting inert gas into the cap skirt volume. 16) Anapparatus as recited in claim 15, wherein the first inert gas and thesecond inert gas differ in chemical composition. 17) An apparatus asrecited in claim 11, further comprising a header block connected to theinert gas supply, and wherein the means for injecting the inert gas intothe container head space and the means for injecting the inert gas intothe cap skirt volume are connected to the header block.